Insulator



March 31, 1931. G, A. BURNHAM INSULATOR Original Filed Aug. l

'a substantial monetary loss.

Patented Mar. 31, 1931 UNITED STATES PATENT oFFlcl-z GEORGE A. BUBNHAM, OF SAUGUS, MASSACHUSETTS, ASBJIGNOB, BY MESNE ASSIGN- MENTS, T0 CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF BOSTON, MAS- SACHUSETTS, A CORPORATION OF MASSACHUSETTS INSULATOR Application led August 1, 1924, Serial No.l 729,625. Renewed August 10, 1929.

`within the bushing, whereupon the entire in-` sulator, usually, must be cast aside and replaced -by an electrically-sound insulator. Such insulators are relatively expensive and the failure of an insulator may represent This type of insulator cannot, ordinarily, be repaired so that, if the insulator fails, and a spare insulator is not on hand, the electrical apparatus may be out of commission for a substantial length of time. Consequently, a supplyof spare insulators are sometimes maintained on hand from which a faulty insulator may be replaced, which necessitates a considerable monetary investment.

An object of this invention is the provision of a relatively inexpensive bushin type insulator and one in which the insu ating element most likely to fail in use is relatively inexpensive and is so arranged that it may be withdrawn and replaced by a fresh element.

A further Objectis the provision of a renewable insulated current-conducting element for a bushing-type insulator.

A further object is generally to improve the construction of electric insulators.

Fig. 1 is a vertical sectional elevation through a bushing-type insulator embodying the invention.

Fig. 2 is a side view of a renewable insulated current-conducting element for the' insulater.

The insulator embodying the invention may be used with any desirable type of electrical apparatus, and is here shown adapted eS- pecially for an oil immersed electric switch.

The insulator includes the substantially vertical metal tube or shell 10 which is of substantial length and diameter and is adapted to enclose the insulated current conductor. Said tube may be formed or provided with a supporting flange 11 intermediate= its ends, by which flange the insulator may be attached securely to a sup ort 12, which support may be the cover oi) an oil receptacle. The lower end of the tube ma7 extend beneath the surface of the oil an the upper end of the tube may extend for a substantial distance above the attaching flange 11, and the cover 12.

An insulating cap may be applied to the open upper end of said tube and said cap may include the substantially cylindrical body 15 and the integral outstanding and depending flange or petticoat 16, both made of some suitable insulating materiell, as porcelain. Said cylindrical body 15 is or may be formed with an internal axial recess therein in which the upper end of said tube 10 is received, and said cap may be secured permanently to said tube by the cement 17, which cement forms a fluid-tight seal between the tube and the insulating cap. Said axial recess is reduced and continued in the recess 18, which recess extends within the cap for a substantial distance above and approximately co-axially with the internal bore of the tube l0. The top of the insulating cap may be formed or provided with a boss 19 over which a metal cap 20 may be disposed and to which said cap may abe fixed. Said metal cap and said boss may have aligned passages 21 and 22 which are also in ali nment with the recess 18 and the bore of said tube 10. Said cap may be formed or provided with the externally-screwthreaded boss 23 through which said passage 21 extends.

A hollow and conical insulating cap 25 is disposed over the'lower open end of said tube 10 and extends for a substantial distance therebelow. The upper end of said insulating cap may be fixed to an annular metal ring 26, which ring may loosely surround the lower end of said tube 10 and be detachably secured, by suitable means as screws 27, to an outstanding flange 28 carried by the lower end of said tube, whereby said insulating cap may be removed from said tube 10, when desired, thereby to expose the lower open end of the tube. An attaching member 30 is passed through and fixed in the end of said insulating cap and -has a recess 31 therein adapted to receive the current-conducting member hereinafter to be described. A set screw 33 or other suitable clamping means may serve to attach the conductin member securel to said member 30; and said set screw may e accessible through an opening 34 in the side wall of said cap 25. The lower or outer end of said attaching member 30 may be suitably formed and arranged to engage an electric conductor and, as here shown, is provided with a relatively massive at head 35 arranged to function as a contact member and to be engaged by a movable contact member, not s own, of an electric switch.

The renewable insulated conducting element also embodying the invention includes a substantially straight conductor 40 of substantial length and diameter, which is here shown as composed of a pluralit of strands of smaller conductors, althoug it may be constructed otherwise. The conductor has a body of insulating material 42 applied to it, to cover it substantially from end to end but to leave exposed the free ends of the conductor. The insulating material may be an impregnated paper, for instance, which may be wound tightly about the conductor to produce a thickness of insulation adequate to withstand the potential adapted to be impressed on the conductor. The ends of the insulating body may be tapered down to the exposed ends of the conductor, as at 44, and the ta ered ends may be covered with an insulating tape 45, whereby to seal the exposed convolutions of the insulating material. The substantially cylindrical body of the insulation may be, and preferably is, enclosed tightly in a conducting sheath, as the lead sheath 46, for protection of the insulation and also to enhance the electrical properties of the unit, said sheath serving to dlstribute more uniformly the electrostatic stress 'on the insulation and to prevent the formation of corona in the spaces between the tube 10 and the insulated conductor.

The insulated conductor is disposed within the tube 10 in the manner indicated in Fig. 1.

The conducting sheath 46 preferably is substantially co-extensive the length of said tube or shell 10 and may be electrically connected with it by suitable means as the spring-finger 48 attached to the inner wall of said tube by `the screw 49 and extended inwardly within said tube to bear against said sheath. The lower tapered end of the linsulated conductor is disposed within the body of the conical insulating cap 25 and below the oil level and the lower ex osed end of the conductor is received within the recess 31 of and securely attached detachably to and electrically con nected with the attaching member 30. The up r tapered end of the insulated conductor is isposed within the recess 18 of the upper insulating cap and, preferably, above the top of said tube 10 and the exposed end of the conductor is extended through the passages tork of t e insulator, the tube 10 and its insulating caps is removed from the support 12 and the lower insulating cap 25 is removed, whereb to permit a new insulated conductor to e inserted within the tube and attached to the upper cap. The lower cap is then secured to the lower end of the tube and connected with the lower end of the conductor.

The insulation carried by the conductor unit is the only part of the insulator likely to fail in use and the unit is relatively inexpensive in construction and consequently a suppl of spare units may be maintained on han to replace a faulty unit, for a relatively small monetary investment.

For commercial reasons, I prefer to form the insulated conductor units, as above set forth and as illustrated in Fig. 2, from the commercial high tension cable, which cable, as is well known, comprises an inner conductor, an intermediate insulator, and an outer lead sheath, as illustrated and described in connection with Fig. 2. The cable is cut in short sections of suitablelength, the end portions of the lead sheath are cut away to .leave only the short section illustrated, and

rounding and in intimate contact with said conductor between its ends, and a ilexible metallic sheath carried by and in intimate contact with and enclosing the ma'or portion of the length of said insulating dy.

2. A bushingfype insulator com rising the combination o a conducting shell aving insulatin end-portions, conducting attaching mem rs carried by sa'iid.endportions,`

incase? ducting attaching members and a conductingunit disposed within said shell comprising a conductor extended between the attaching members of said insulatin end-portions of said shell, a body of insulatlon carried by and enclosing and in intimate contact with the major portion of said conductor, and an ex-l ternal conducting sheath carried by and enclosing and in intlmate contact with the major portion of said body of insulation.

4. A bushing-type insulator comprising the combination of a conducting shell having insulating end-caps, one of which has a removable connection with said shell, conducting attaching members carried by said endcaps, and a removable conducting unit disposed within said shell comprising a lconductor having exposed ends connected detachably with said attaching-members, a body of insulation carried `by and enclosing and in intimate contact with said conductor between its ends, and an external conducting sheath carried by and enclosing and in intimate contact with said body of insulation and terminated shortl of the exposed ends of said conductor.

5. A'bushing-type insulator comprising the combination of a conducting shell, insulating end-caps carried by the ends of said shell, one of which has a removable connection with l said shell, conducting attaching members carried by said end-caps, anda removable conducting unit disposed within said shell comprising a conductor having exposed ends connected detachably with said attachingmembers, a substantially cylindrical body of insulation carried by and enclosing said conductor between the exposed ends thereof and having tapered end-portions, and a conducting sheath carried by and enclosing the substantially cylindrical portion of said body of insulation.

6. A bushing-type insulator comprising the combination of a conducting shell, internally-recessed insulating caps carried by and extended beyond the ends of said shell, one of said caps having means to expose the interior of said shell, attaching members carried by said caps, and a conducting unit disposed removably within said shell comprising a conductor having end-terminals extended through said insulating end-caps and connected with said attaching membersz a sub- Y stantially cylindrical bod of insulatlon carried b and enclosing sai conductor between its en terminals, said body of insulation having tapered end-portions disposed within the recesses in said end caps, and a conducting sheath enclosin the substantially cylindrical portion of saidody ofinsulation.

7. A reillable bushin -type insulator comprising a conducting s ell, insulating endcaps carried by the ends of said shell, one of which has adetachable connection with said shell, terminal members carried by said endcaps, and an insulated conducting unit disposed removably within said shell comprising a conductor having detachable connections with said terminal members, a bodyof insulation carried by and enclosing said conductor between said terminal members, and a conductin sheath carried by and enclosing said body o insulation and terminated short of the ends thereof and havin a detachable ellleflarical connection with sald conducting s e 8. A high tension insulating bushing comprising a tubular member having insulated terminal members at the ends thereof, and a section of flexible commercial metallicsheathed, high tension cable received in said tubular member and having the exposed opposite ends of its conductor connected with said insulated terminal members and constituting the electric conductor of said bushing, the insulation of said cable constituting at least a substantial part of the insulation of said bushing.

9. A high tension insulating bushing comprising a tubular member having insulated terminal members at the ends thereof, and a section of iexible commercial, metallicsheathed, high tension cable received in said tubular member and having the exposed opposite ends of its conductor connected with said insulated terminal members and constituting the electric conductor of said bushing, the insulation of said cable constituting at least a substantial part of the/insulation of said bushing, and means to ground the metal sheath of said cable.

10. The combination with a bushing type insulator including an enclosing casin having terminal connectors, of a section o iiexible metallic-sheathed high tension cable forming the insulated conducting unit within the casing and having exposed end conductorterminals connected with said bushing terminal connectors.

11. The combination of a casing containing an insulating fluid, a' metal tube extending into said casing, an insulator carried by said tube at one end immersed in said insulating fluid, a terminal member carried by said insulating member, an insulated terminal member at the opposite end of said tube, and a flexible metal sheathed cable disposed within 4j incase? said tube and havinl the ends of its conduc- 'tor connected to sai terminals and its insulation immersed in said insulation fluid.

12. The combination of a casing contain# ing an insulating fluid, a metal tube extendin into said casin an insulator carried b sai tube at one en immersed in said' insu ating y lfluid, a terminal member carried b said in-r sulating member, an insulated terminal member at the o posite end of said tube, and a exible meta sheathed cable disposed within said tube and having the ends of its con'- ductor connected to said terminals and its metal sheath and insulation immersed in said u insulating fluid. In testlmony whereof, I have signed m name to this specification.

GEORGE A. BURNHAM. 

